Maintaining Your Hydraulic Stabilizer System

Once reserved for large commercial and military vessels, hydraulic stabilizer systems are now standard equipment on pleasure yachts of all types and sizes. There are a number of different types of hydraulic stabilizer systems but the most common ones we see at High Seas Hydraulics use fins to stabilize the boat. The fins are located on either side of the boat and stick out into the hull envelope which is the area of water that would be contained if lines from a boat’s keel and gunwale met to form a right angle below the water. They use gyros or electronic motion sensors to detect even the slightest bit of movement in the water and command the fins to rotate accordingly. So, for example, if the boat’s rolling to starboard, the fins will turn counterclockwise to counteract that motion. The fins can be used underway, where they can reduce roll up to 90 percent.  Some units are also designed for “at rest” stabilization, where the reduction is closer to 70 percent.

Maintaining your hydraulic stabilizer system is critical to your cruising safety and comfort. In general, NAIAD®, a popular brand of fin stabilizer systems, recommends that lower seals in the units be changed every three years or 4,000 operating hours. However, a major overhaul is highly recommended anytime there is water found in the grease beyond the outer shaft seal or there is signs of grease oozing up from the inner seals around the stabilizer shaft. Once salt water compromises the grease, the bearings will start to deteriorate and the grease needs to be replaced.

Annual maintenance on hydraulic stabilizer systems should include:

  • Changing the oil filters
  • Inspecting, on a monthly basis, the zinc anodes and replacing as needed
  • Servicing the cooling water pump annually or as needed in the case of problems
  • Checking the bonding agents to ensure a good seal
  • Inspecting the fin actuators for bushing or bearing wear or noises
  • Checking the entire hydraulic stabilizer system for hydraulic leaks

The above maintenance items can be done while the vessel is in the water and does not require a haul out.

As mentioned above, the lower seals should be replaced every three years which requires the vessel to be hauled in order to;

  • Remove the fins (make sure the fins are pinned on center prior to haul-out)
  • Remove and replace lower lip seals
    • Inspecting grease at the same time
  • Reinstalling fins centered to the keel and torqued.

When more comprehensive service is required, every 10 years or if there is water intrusion into the grease, the process would include removing the fins from the boat, taking apart the cylinders, inspecting the potentiometer, removing the top plate, tiller arm, hoses and shaft. Once we remove the fins from the boat we would:

  • Remove all the old grease from the bearing housings
  • Remove the bearing braces mounted in the housing
  • Inspect the housings for abnormal wear
  • Rebuild the actuator cylinders if required
  • Replace all of the hydraulic hoses at the stabilizer unit
  • Replace all of the trunnion bushings and bearings for the cylinders
  • Clean all surfaces of the top plate and inner hall plate
  • Run a tap into all mounting hardware to clean them out for reassembly
  • Inspect all mounting hardware to clean and replace as necessary
  • Replace all inner and outer seals
  • Reassemble the unit

The upper and roller bearings are installed on the shaft. So when the shaft is removed, the roller bearings stay with it. The roller bearings are cut off the shaft in our machine shop, Straight Line Marine. Next the shaft is polished in a lathe and inspected for corrosion or scarring in the lip seal area. If we do find corrosion, we will clad  the corroded area. Once the work on the shaft is complete, we will install new bearings using heat to avoid scoring the shaft.

Once the vessel is launched, we will bring up the electronic side of the system and test or reset the potentiometers. It is usually not until this late stage in the project that we can determine if the potentiometers need to be replaced.

Once we completed all the steps, we re-assemble the hydraulic stabilizer system and re-install it back in the boat.

While this process closely follows the recommended procedures for a NAIAD 505 service plan, it is fairly typical for any fin-type hydraulic stabilizer system.

At High Seas Hydraulics, we also have the ability of make hydraulic hoses in-house up to 1-1/4 inches in diameter and stock common hoses and fittings to make service and maintenance easier and quicker on this units. We also have the ability to re-build custom cylinders with the help of our in-house machine shop.

High Seas Hydraulics is a member of the High Seas family of marine companies that for 30 years has serviced marine propulsion systems in South Florida.